Aquaculture of the green mussel, Mytilus viridis Linnaeus, in Malaysia

Abstract

Successful induced spawning of the mussel, Mytilus viridis Linnaeus, was obtained primarily through a combination of four 20-min temperature cycles between 25 and 35°C in a seawater medium containing 0.2% NH 4OH. Artificial fertilization and life cycle studies indicated the usual life cycle observable for all mussel species. Natural spawning was found to occur twice a year in the months of March and April and October and November, in close association with the monsoon seasons of this region. Physiologically, the species has a 50% survival salinity tolerance at 24 and 80‰, 50% survival temperature tolerance at 10 and 35°C and 50% pH survival tolerance at pH 3.5 and 9 for periods of 2 weeks. These values are fairly wide in range when compared to those for the European mussel, Mytilus edulis Linnaeus. However, its optimum level of salinity, temperature and pH for normal growth are between 27 and 65‰, 26 and 32°C and 6 and 8.2, respectively. Conditions in the local waters are such that they are fairly saturated in oxygen, ca 6 ml/l, primary productivity is 5.2 μg chlorophyll/l, water temperatures are high the year through, ca 29.5°C, and salinity is high, ca 32‰. These factors are extremely favourable for mussel culture so that the local species, Mytilus viridis Linnaeus, attains marketable size within 7–8 months which is about twice as fast as the European mussel. Nutrition studies also indicated this species attains a high protein content at harvesting time, ca. 18%, which is fairly high compared to the European mussel's value of 9–13% of the wet weight. Its raw flesh to shell weight ratio is ca 60% which is also pretty high compared to the European mussel's ratio of 49–50%. Different modes of culture tried out indicated that the suspended rope culture technique, practised efficiently in other parts of the world, is the most productive method in this region. Of the few collectors used to collect spat from natural spatfalls, meshed nylon netting seemed promising, through expensive. Intestinal content studies indicated that the mussel, Mytilus viridis Linnaeus, selectively ingested the diatom, Coscinodiscus nodulifer A. Schmidt, the dominant phytoplankton in the waters around the culture station, which has no toxic effects for humans on consumption.